kernel: disable cfi cmdset 0002 erase suspend

on some platforms, erase suspend leads to data corruption and lockups when write
ops collide with erase ops. this has been observed on the buffalo wzr-hp-g300nh.
rather than play whack-a-mole with a hard to reproduce issue on a variety of devices,
simply disable erase suspend, as it will usually not produce any useful gain on
the small filesystems used on embedded hardware.

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@27984 3c298f89-4303-0410-b956-a3cf2f4a3e73